## FACT

`FACT`

, which computes factorials, is surprisingly not categorized as Statistical. Instead, you'll find it on the Math & Trig Functions menu. It's easy to use. Supply it with a number, and it returns the factorial. Here are the steps:
- Select a cell for
`FACT`

's answer. - From the Math & Trig Functions menu, select
`FACT`

to open its Function Arguments dialog box. - In the Function Arguments dialog box, enter the appropriate value for the argument. In the Number box, type the number whose factorial you want to compute. The answer appears in the dialog box. If you enter 5, for example, 120 appears.
- Click OK to put the answer into the selected cell.

## PERMUT and PERMUTIONA

`PERMUT`

enables you to calculate *. Here's how to use it to find*

_{N}P_{r}_{26}

*P*

_{5}, the number of 5-letter sequences (no repeating letters) that you can create from the 26 letters of the alphabet. In a permutation, remember,

*abcde*is considered different from

*bcdae.*Follow these steps:

- Select a cell for
`PERMUT`

's answer. - From the Statistical Functions menu, select
`PERMUT`

to open its Function Arguments dialog box. - In the Function Arguments dialog box, type the appropriate values for the arguments.
In the Number box, enter the
*N*in. For this example,_{N}P_{r}*N*is 26. In the Number_chosen box, enter the*r*in. That would be 5. With values entered for both arguments, the answer appears in the dialog box. For this example, the answer is 7893600._{N}P_{r} - Click OK to put the answer into the selected cell.

`PERMUTIONA`

does the same thing, but with repetitions allowed. Its Function Arguments dialog box looks exactly like the one for `PERMUT`

. Its answer is equivalent to N^{r}. For this example, by the way, that answer is 1181376.

## COMBIN and COMBINA

`COMBIN`

works pretty much the same way as `PERMUT`

. Excel categorizes `COMBIN`

and `COMBINA`

as Math & Trig functions.Here's how you use them to find _{26}C_{5}, the number of ways to construct a 5-letter sequence (no repeating letters) from the 26 letters of the alphabet. In a combination, *abcde* is considered equivalent to *bcdae*.

- Select a cell for
`COMBIN`

- From the Math & Trig Functions menu, select
`COMBIN`

to open its Function Arguments dialog box. - In the Function Arguments dialog box, type the appropriate values for the arguments.
In the Number box, enter the
*N*in. Once again,_{N}C_{r}*N*is 26. In the Number_chosen box, enter the*r*in. And again,_{N}C_{r}*r*is 5. With values entered for both arguments, the answer appears in the dialog box. For this example, the answer is 65870. - Click OK to put the answer into the selected cell.

`COMBINA`

. Its Function Arguments dialog box looks just like `COMBIN`

’s. For this example, its answer is equivalent to _{30}C

_{25}(142506).